Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/0087—Galenical forms not covered by A61K9/02 - A61K9/7023
  • A61K9/0095—Drinks; Beverages; Syrups; Compositions for reconstitution thereof, e.g. powders or tablets to be dispersed in a glass of water; Veterinary drenches
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/13—Amines
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/33—Heterocyclic compounds
  • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
  • A61K31/40—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having five-membered rings with one nitrogen as the only ring hetero atom, e.g. sulpiride, succinimide, tolmetin, buflomedil
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/2004—Excipients; Inactive ingredients
  • A61K9/2013—Organic compounds, e.g. phospholipids, fats
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/2004—Excipients; Inactive ingredients
  • A61K9/2022—Organic macromolecular compounds
  • A61K9/205—Polysaccharides, e.g. alginate, gums; Cyclodextrin
  • A61K9/2054—Cellulose; Cellulose derivatives, e.g. hydroxypropyl methylcellulose
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/2095—Tabletting processes; Dosage units made by direct compression of powders or specially processed granules, by eliminating solvents, by melt-extrusion, by injection molding, by 3D printing
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/28—Dragees; Coated pills or tablets, e.g. with film or compression coating
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
  • A61P25/28—Drugs for disorders of the nervous system for treating neurodegenerative disorders of the central nervous system, e.g. nootropic agents, cognition enhancers, drugs for treating Alzheimer's disease or other forms of dementia
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/30—Against vector-borne diseases, e.g. mosquito-borne, fly-borne, tick-borne or waterborne diseases whose impact is exacerbated by climate change

Definitions

• the present invention is directed to pharmaceutical solid, oral dosage forms of compositions of 1-aminocyclohexane compounds which exhibit an immediate release profile, possess advantageous stability profiles and additionally disintegrate rapidly in aqueous solutions.
• the invention is particularly suitable for solid pharmaceutical dosage forms of 1- aminocyclohexane compounds in which a therapeutically effective amount of the active ingredient is available in the use environment shortly after administration.
• These compositions can be provided as dispersible tablets for administration as aqueous oral solution.
• the active ingredient is preferably, the 1-aminocyclohexane, memantine.
• the 1-aminocyclohexane is neramexane.
• 1-Aminocyclohexanes such as Memantine (l-amino-3,5-dimethyladamantane) and neramexane (l-amino-l,3,3,5,5-pentamethylcyclohexane), are moderate affinity, uncompetitive
• NMDA receptor antagonists with strong voltage dependency and rapid blocking/unblocking kinetics. Therefore, there is an existing and continual need in the art for solid oral formulations of 1-aminocyclohexane compounds, and more preferably memantine HCl (l-amino-3,5- dimethyladamantane hydrochloride) and neramexane mesylate (l-amino-1,3,3,5,5- pentamethylcyclohexane mesylate).
• memantine HCl l-amino-3,5- dimethyladamantane hydrochloride
• neramexane mesylate l-amino-1,3,3,5,5- pentamethylcyclohexane mesylate
• Solid oral drug compositions or preparations have various release profiles such as an immediate release profile as referenced by FDA guidelines ("Dissolution Testing of Immediate Release Solid Oral Dosage Forms", issued 8/1997, Section IV-A) or an extended release profile as referenced by FDA Guidelines ("Extended Release Oral Dosage Forms: Development, Evaluation, and Application of In Vitro/In Vivo Correlations", Food and Drug Administration, CDER, September 1997, Page 17).
• FDA guidelines Dissolution Testing of Immediate Release Solid Oral Dosage Forms
• FDA Guidelines Extended Release Oral Dosage Forms: Development, Evaluation, and Application of In Vitro/In Vivo Correlations", Food and Drug Administration, CDER, September 1997, Page 17.
• immediate release solid dosage forms permit the release of most or all of the active ingredient over a short period of time, such as 60 minutes or less, and make rapid absorption of the drug possible.
• extended release solid oral dosage forms permit the release of the active ingredient over an extended period of time in an effort to maintain therapeutically effective plasma levels over similarly
• U.S. Patent No. 5,382,601 provides solid pharmaceutical dosage forms containing memantine, which exhibit an extended two-phase release profile, with a portion of the drug being released immediately, followed by a sustained release of the remainder.
• the matrix of this formulation contains both a water-soluble and a water-insoluble salt of casein, preferably sodium and calcium caseinate.
• casein has an unpleasant taste; it is associated with the undesirable effect of exacerbating some side effects as disclosed in U.S. Patent No. 6,413,556; and displays instability in varying pH.
• Another concern regarding casein is the possibility of Bovine Spongiform Encephalitis (BSE) contamination or transmission of another infectious agent since casein is an animal-derived product.
• BSE Bovine Spongiform Encephalitis
• NMDA N-methyl-D-aspartate
• U.S. Patent No. 6,194,000 A general method of preparing modified release N-methyl-D-aspartate (NMDA) receptor antagonists was described in U.S. Patent No. 6,194,000. This method involves preparing an instant release component and a modified release component to arrive at the final formulation.
• the patent discloses the formulations consisting of encapsulated beads previously coated using organic solvent-based systems. However, this patent does not specifically disclose compositions containing memantine or neramexane. The patent also does not teach how the release rates affect the T n ⁇ x (time to maximum plasma concentration) or that this procedure will result in dose-proportional formulations. Currently, a dosing regime of memantine of twice a day is employed using non-dose proportional immediate release tablets.
• memantine After oral administration in man, memantine is completely absorbed (absolute bioavailability of approximately 100%).
• the time to maximum plasma concentrations (T max ) following oral doses of 10 to 40 mg memantine ranged between 3 and 7 hours, with peak plasma concentrations (C max ) after a single 20 mg oral dose ranging between 22 and 46 ng/mL.
• the AUC and C max values of memantine increase proportionally with dose over the dosage range of 5 to 40 mg.
• the elimination half-life (T /2 ) of memantine is approximately 60-80 hours.
• dose-proportional memantine formulations which are readily achieved with immediate release formulations.
• Advantages of immediate release, dose-proportional formulations include improved ease of administration by allowing increases in dose without increasing the number of tablets that need to be administered, and increased flexibility in drug administration by allowing the target drug to be administered either as multiples of lower strength formulations or as one higher strength formulation.
• Another advantage of dose- proportional formulations of highly soluble and highly permeable drugs, particularly that of memantine and neramexane, is that the bioavailability of multiple strengths, e.g., 10 mg versus 80 mg, are considered identical and in accordance with the guidelines, "Waiver of In Vivo Bioavailability and Bioequivalence Studies for Immediate-Release Solid Oral Dosage Forms Based on a Biopharmaceutics Classification System", U.S. Department of Health and Human Services, Food and Drug Administration. Administration of increasing drug doses are often required as part of an up-titration regimen to the desired therapeutic dose because such regimens result in improved tolerability.
• 1-aminocyclohexanes such as memantine (l-amino-3,5-dimethyladamantane) and neramexane (l-amino-1,3,3,5,5- pentamethylcyclohexane), and their salts, including the hydrochloride, hydrobromide, mesylate salt as well as other pharmaceutically accepted salts, can be formulated into an immediate release dosage form with dose-proportional bioavailability and advantageous stability profiles where dosage forms preferably disintegrate rapidly.
• the formulation of the present invention includes 1-aminocyclohexanes, such as Memantine (l-amino-3,5-dimethyladamantane) and neramexane (l-amino-1,3,3,5,5- pentamethylcyclohexane), an optionally pharmaceutically acceptable coating, and one or more excipients to be administered in a single oral dosage form, preferably once a day.
• the dosage form may be administered twice a day, with about 4 to about 8 hours between each administration.
• the dosage form is a tablet or an aqueous solution of the dispersed tablet.
• the present invention provides a dosage form which immediately releases the active agent, for example memantine or neramexane, at a rate of about 80% or more within the first 60 minutes following entry of the dosage form into a use environment.
• the dosage form is released to this extent within the first 30 minutes, more preferably, within the first 15 minutes.
• the T max for memantine containing dosage forms is achieved at a time interval averaging from about 3 hours to about 7 hours after entry of the dosage forms into the use environment.
• the time interval averages between about 4 hours to about 6 hours.
• the T max for neramexane containing dosage forms is achieved at a time interval averaging from about 2 hours to about 8 hours after entry of the dosage form into the use environment.
• the time interval averages between about 3 to about 8 hours.
• the active ingredient of the present invention is usually present in amounts ranging from about 2 % w/w to about 20% w/w. Preferably, the amounts range from about 3.2 % w/w to about 10 % w/w, more preferably from about 3.9 % w/w to about 8.4 % w/w, based on the weight of the entire dosage form. In specific embodiments where the active ingredient is neramexane mesylate, the active ingredient of the present invention is usually present in amounts ranging from about 2 % w/w to about 50% w/w.
• the amounts range from about 2 % w/w to about 40 % w/w, more preferably from about 3 % w/w to about 25 % w/w.
• the preferred optional pharmaceutically acceptable coating contains hydroxypropyl methylcellulose, such as Opadry ® (Colorcon, West Point, PA) or Sepifilm ® (Seppic, NJ) present in amounts ranging from about 2 % w/w to about 7 % w/w, preferably from about 2 % w/w to about 5 % w/w.
• the formulation contains fillers such as starch and starch derivatives, hydrated sugar alcohols, calcium phosphates, and cellulose based excipients and derivatives thereof.
• the oral dosage form of the present invention may further comprise one or more pharmaceutically acceptable carriers, excipients, anti-adherants, stabilizing agents, binders, colorants, disintegrants, glidants, and lubricants.
• the dosage forms contain excipients that have improved stability, forming less than 3.0 % w/w lactose adduct, preferably less than 2.5 % w/w, upon storage for 36 months at room temperature.
• the present invention discovered the lactose adduct formation, which was not a foreseen adduct formation reaction.
• an adduct such as a lactose adduct, is formed by a Maillard reaction between the 1-aminocyclohexane analog active ingredient and a lactose excipient.
• the dosage forms contain the filler microcrystalline cellulose, which is present in amounts ranging from about 10% w/w to about 35 % w/w, wherein the compositions additionally comprise lactose monohydrate, preferably, from about 18 % w/w to about 22 % w/w. Such dosage form exhibits less than 3 % adduct formation, in 36 months.
• the microcrystalline cellulose filler is present in amounts ranging from about 20 % w/w to about 95 % w/w, preferably, in amounts ranging from about 60 % w/w to about 90 % w/w.
• Such dosage forms exhibit less than 0.5 % adduct formation in 36 months.
• the dosage forms contain the lubricant magnesium stearate, which is present in amounts ranging from about 0 % to about 2% w/w, preferably, in amounts ranging from about 0.2 % to about 0.5 % w/w.
• the dosage forms contain an excipient which supports the disintegration of the formulation. This excipient may be starch-based or derivatives thereof, cellulose-based or derivatives thereof, or based on pyrrolidone or a derivative thereof, in amounts ranging from about 0.2 to 10 % w/w.
• the composition is in tablet form.
• the tablet form has a hardness of from about 3 to about 40 Kp.
• the hardness is from about 4 to about 30 Kp.
• hardness of the tablet is also related to shape and size of tablets.
• Figure 1 is a plot of the mean plasma concentrations of memantine (ng/mL) following administration of two- 10 mg memantine HCl immediate release tablets of the present invention four hours apart (closed circle) in young healthy male and female subjects over time (hours) elapsed from administration. Also shown in the plots are results of two modified release tablets (open circle and inverted triangle).
• Figure 2 is a plot of the log of the mean plasma concentrations of memantine (ng/mL) following administration of two- 10 mg memantine HCl immediate release tablets four hours apart (Treatment A, 30 min release) (closed circle), or modified release tablets (Treatments B and C, 6 hour and 12 hour release) tablets (open circle and inverted triangle), in young healthy male and female subjects against time elapsed (hours) from administration.
• Figure 3 is a plot of mean plasma concentrations of memantine (ng/mL) following administration of two 10 mg memantine HCl immediate release tablets of the present invention four hours apart (Treatment A) (closed circle) or modified release tablets prepared using a matrix formula containing HPMC (Treatments B and C) (open circle and inverted triangle) in young healthy male and female subjects against time (hours) for the first 24 hours following administration.
• Figure 4 depicts the dissolution of 5 mg memantine HCl tablets. Dissolution is shown as the percent dissolved over time (hours).
• Figure 5 depicts the dissolution of 10 mg memantine HCl tablets. Dissolution is shown as the percent dissolved over time (hours).
• Figure 6 depicts the dissolution of 15 mg memantine HCl tablets. Dissolution is shown as the percent dissolved over time (hours).
• Figure 7a depicts the dissolution of 20 mg memantine HCl tablets, Lot A. Dissolution is shown as the percent dissolved over time (hours).
• Figure 7b depicts the dissolution of 20 mg memantine HCl tablets, Lot B. Dissolution is shown as the percent dissolved over time (hours).
• Figure 8 depicts the dissolution of 80 mg memantine HCl tablets. Dissolution is shown as the percent dissolved over time (hours).
• Figure 9 plots the dissolution of memantine with microcrystalline cellulose (i.e., without lactose) at a 5 mg strength using Prosolv ® (a mixture of microcrystalline cellulose and colloidal silicone dioxide) and at a 20 mg strength using Avicel ® (microcrystalline cellulose) against time (hours) from administration.
• Prosolv ® a mixture of microcrystalline cellulose and colloidal silicone dioxide
• Avicel ® microcrystalline cellulose
• an immediate release pharmaceutical composition for the administration of a 1-aminocyclohexane, preferably memantine or neramexane, and pharmaceutically acceptable salt thereof, to a human or animal subject, where the composition includes oral solid dosage forms, preferably in tablet form.
• the pharmaceutical compositions comprise a therapeutically effective amount of a 1-aminocyclohexane, preferably memantine (free base) or neramexane (free base), or a pharmaceutically acceptable salt thereof, preferably the HCl salt and optionally a pharmaceutically acceptable coating, as well as, optionally, one or more carriers, fillers, anti- adherants, excipients, stabilizing agents, binders, colorants, disintegrants, glidants, and lubricants (all pharmaceutically acceptable).
• a 1-aminocyclohexane preferably memantine (free base) or neramexane (free base)
• a pharmaceutically acceptable salt thereof preferably the HCl salt and optionally a pharmaceutically acceptable coating
• one or more carriers fillers, anti- adherants, excipients, stabilizing agents, binders, colorants, disintegrants, glidants, and lubricants (all pharmaceutically acceptable).
• Memantine (l-amino-3,5-dimethyladamantane) and neramexane (l-amino-1,3,3,5,5- pentamethylcyclohexane) can be considered an analog of 1-amino-cyclohexane (disclosed, e.g., in U.S. Patent Nos. 4,122,193; 4,273,774; 5,061,703), and are systemically-active noncompetitive NMDA receptor antagonists having low to moderate affinity for the receptor and strong voltage dependency and rapid blocking/unblocking kinetics.
• Memantine and neramexane are indicated for treatment of CNS diseases such as Alzheimer's disease.
• Memantine has been approved in the United States for the treatment of Alzheimer's Disease and is currently approved outside the United States as an oral formulation for the Alzheimer's Disease and Parkinson's Disease and has been available commercially since 1982. It is currently under investigation for the treatment of neuropathic pain.
• the 1-aminocyclohexane compounds of the present invention having NMDA- antagonistic activity can be represented in the general formula (I):
• A is selected from the group consisting of linear or branched lower alkyl (C 1 -
• CoXlinear or branched lower alkenyl (C 2 -C 6 ), and linear or branched lower alkynyl (C 2 -C 6 );
• R 1 and R 2 are independently selected from the group consisting of hydrogen, linear or branched lower alkyl (C 1 -C 6 ), linear or branched lower alkenyl (C 2 -C 6 ), linear or branched lower alkynyl (C 2 -C 6 ) aryl, substituted aryl and arylalkyl;
• R 3 and R 4 are independently selected from the group consisting of hydrogen, linear or branched lower alkyl (C 1 -C 6 ), linear or branched lower alkenyl (C 2 -C 6 ), and linear or branched lower alkynyl (C 2 -C 6 ), or together form alkylene (C 2 -Ci 0 ) or alkenylene (C 2 -Cio) or together with the N form a 3-7-membered azacycloalkane or azacycloalkene, including a substituted (alkyl (Ci-C 6 ), alkenyl (C 2 -C
• R is independently selected from the group consisting of hydrogen, linear or branched 0 lower alkyl (Ci-C 6 ), linear or branched lower alkenyl (C 2 -C 6 ), and linear or branched lower alkynyl (C 2 -C 6 ), or R 5 combines with the carbon to which it is attached and the next adjacent ring carbon to form a double bond;
• R p , R q , R r , and R s are independently selected from the group consisting of hydrogen, linear or branched lower alkyl (Ci-C 6 ), linear or branched lower alkenyl (C 2 -C 6 ), linear or
• R q , R r , and R s independently may form a double bond with U or with Y or to which it is attached, or R p , R q , R r , and R s may combine together to represent a lower alkylene -(CH 2 ) X - or a lower alkenylene bridge wherein x is 2-5, inclusive, which alkylene bridge may, in turn, combine with
• R 5 to form an additional lower alkylene -(CH 2 ) y - or a lower alkenylene bridge, wherein y is 1-3, d inclusive; and the ring defined by U-V-W-X-Y-Z represents an optionally unsaturated cyclohexane ring wherein U, W, and Y represent carbon atoms and V, X , and Z each independently represent a carbon atom, CH, or CH2, (or the definitions of U, W, Y on one hand and V, X, and Z can be reversed including corresponding placement of the R groups R*, R 5 , R p , R q , R r , and R s ) it being ) understood that the valence requirements of the ring atoms are respected, and include optical isomers, diastereomers, polymorphs, enantiomers, hydrates, pharmaceutically acceptable salts, and mixtures of compounds within formula (I).
• the ring defined by U-V-W-X-Y-Z is preferably selected from the group consisting of cyclohexane, cyclohex-2-ene, cyclohex-3-ene, cyclohex-l,4-diene, cyclohex-l,5-diene, ) cyclohex-2,4-diene, and cyclohex-2,5-diene.
• Compounds of Formula I may be adamantyl substances.
• Non-limiting examples of 1-aminocyclohexane compounds used according to the invention include the 1-aminoalkylcyclohexane derivatives selected from the group consisting of:
• Neramexane (l-amino-l,3,3,5,5-pentamethylcyclohexane) is disclosed, e.g., U.S. Patent No. 6,034,134, which is incorporated herein by reference in its entirety.
• R 6 is hydrogen, linear or branched lower alkyl (Ci-C 6 ), linear or branched lower alkenyl (C 2 -C 6 ), linear or branched lower alkynyl (C 2 -C 6 ), aryl, substituted aryl or arylalkyl
• Y is
• Non-limiting examples of 1-aminocyclohexane compounds used according to the invention include 1 -amino adamantane and its derivatives selected from the group consisting of: l-amino-3-phenyl adamantane,
• Memantine (1 -amino-3, 5-dirnethyl adamantane), for example, is the subject matter of U.S. Patents No. 4,122,193 and 4,273,774, both incorporated herein by reference in their entirety.
• Neramexane for example, is the subject matter of U.S. Patent No. 6,034,134, incorporated herein by reference in its entirety.
• the 1 -amino adamantane compounds of formulae lib and Hd, including memantine are generally prepared by alkylation of halogenated adamantanes, preferably , bromo- or chloroadamantanes.
• the di- or tri-substituted adamantanes are obtained by additional halogenation and alkylation procedures.
• the amino group is introduced either by oxidation with chromiumtrioxide and bromination with HBr or bromination with bromine and reaction with formamide followed by hydrolysis.
• the amino function can be alkylated according to generally- accepted methods. Methylation can, for example, be effected by reaction with chloromethyl formate and subsequent reduction.
• the ethyl group can be introduced by reduction of the respective acetamide.
• U.S. Patents No. 5,061,703 and 6,034,134 See, e.g., U.S. Patents No. 5,061,703 and 6,034,134. Additional synthetic techniques for the foregoing compounds can be found in published U.S. Application Nos. 2003/0166634 and 2004/0034055, all incorporated by reference in their entirety.
• the 1-aminocyclohexane derivatives of formula (I) may be applied as such or used in the form of their pharmaceutically acceptable salts.
• Suitable salts of the compound include, but are not limited to, acid addition salts, such as those made with hydrochloric, methylsulfonic, hydrobromic, hydroiodic, perchloric, sulfuric, nitric, phosphoric, acetic, propionic, glycolic, lactic pyruvic, malonic, succinic, maleic, fumaric, maleic, tartaric, citric, benzoic, carbonic cinnamic, mandelic, methanesulfonic, ethanesulfonic, hydroxyethanesulfonic, benezenesulfonic, p-toluene sulfonic, cyclohexanesulfamic, salicyclic, p- aminosalicylic, 2-phenoxybenzoic, and 2-acetoxybenzoic acid;
• the salt is memantine hydrochloride (C12H21N ⁇ CI, MW 215.77).
• the salt is neramexane mesylate (Ci 1 H 23 N-CH 4 O 3 S, MW 265.42).
• salts can also include addition salts of free acids. All of these salts (or other similar salts) may be prepared by conventional means. All such salts are acceptable provided that they are non-toxic and do not substantially interfere with the desired pharmacological activity.
• the present invention further includes all individual enantiomers, diastereomers, racemates, and other isomers of those compounds wherein such structural variations are possible.
• the invention also includes all polymorphs and solvates, such as hydrates and those formed with organic solvents, of these compounds. Such isomers, polymorphs, and solvates may be prepared by methods known in the art, such as by crystallization from different solvents, or by regiospecific and/or enantioselective synthesis and resolution, based on the disclosure provided herein.
• the present invention includes derivatives of the compound of the present invention.
• derivatives applicable to the invention include, but are not limited to, structurally related compounds composed of a tricyclic 10-carbon ring bearing an amino group such as nitroxy-memantine derivatives (such as nitroprusside, nitroglycerin, or an NO-generating derivative of nitroprusside or nitroglycerin in U.S. Patent Nos. 5,234,956 and 5,455,279).
• the active ingredient is memantine hydrochloride.
• the active ingredient is present in amounts ranging broadly from about 2.5 mg to about 80 mg, preferably ranging from about 5 mg to about 60 mg.
• compositions contain between about 2% and about 20% w/w memantine; preferably from about 3.2% to about 10% w/w memantine; most preferably from about 3.9 % to about 8.4 % w/w memantine.
• the active ingredient is neramexane mesylate.
• the active ingredient is present in amounts ranging broadly from about 6.25 mg to about 150 mg, preferably ranging from about 12.5 mg to about 125 mg.
• the active ingredient, e.g., neramexane mesylate in the oral dosage form of the present invention is usually present in amounts ranging from about 2 % w/w to about 50 % w/w.
• the amounts range from about 2 % w/w to about 40 % w/w, more preferably from about 3 % w/w to about 25 % w/w.
• the immediate-release dosage form optionally has a coating applied or deposited over the entire surface of a unitary release core.
• Immediate release of the drug is achieved by any of various methods known in the art including the use of a very thin layer or coating, which by virtue of its thinness (i.e., less than about 100 micron) is quickly penetrated by gastric fluid allowing fast leaching of the drug.
• examples of coating materials that rapidly disintegrate and disperse include lactose and microcrystalline cellulose, colloidal silicon dioxide, hydrophilic polymers such as hydroxypropyl methylcellulose, PVA, methacrylates (e.g., Eudragit,® Rohm Pharma Polymer, Piscataway, NJ) natural polymers such as xanthan gum, and combinations thereof (e.g., Prosolv ® , which contains microcrystalline cellulose and colloidal silicone dioxide).
• colloidal silicon dioxide may be necessary in addition to the use of microcrystalline cellulose, e.g., Avicel ® .
• These materials may also be present as excipients in addition to common auxiliary agents and additives or fillers including tabletting aids, colorants, binders, fillers, glidants, and lubricants (all pharmaceutically acceptable).
• hydroxypropyl methylcellulose is used as a coating material.
• the optional coating material is present in amounts ranging from about 1 mg to about 70 mg, preferably from about 3 mg to about 60 mg, more preferably from about 3 mg to about 40 mg.
• compositions contain from about 2% w/w to about 5% w/w coating material containing hydroxypropyl methylcellulose; more preferably from about 2% to about 4% w/w coating material containing hydroxypropyl methylcellulose.
• Fillers or disintegrants act to modify the dissolution pattern.
• fillers include lactose monohydrate, microcrystalline cellulose, Prosolv ® , hydroxypropyl methylcellulose, and combinations thereof. Lactose monohydrate, when used, counterbalances the less soluble ingredients of the composition, thereby acting as a disintengrant, whereas microcrystalline cellulose and similar type filler when employed in a lactose-free environment may require additional disintegrants such as croscarmellose sodium.
• Disintegrants in the dosage forms may further contain an excipient to support the disintegration of the formulation.
• these excipients may be starch based, cellulose based or pyrrolidone based, or a derivative thereof, in amounts ranging from about 0.2 to 10 %.
• hydroxypropyl methylcellulose or ethyl cellulose are used in a matrix tablet, the dissolution rates are much lower than the immediate release rate targeted. This is because the hydrophobic matrix tablets that result when these polymers release the drug by mechanism of polymer erosion. Since the erosion from a hydrophobic matrix is very slow, the dissolution rate of the readily soluble active ingredient is also slow.
• lactose monohydrate in formulation containing memantine, lactose monohydrate is used as a filler. Lactose monohydrate is present in amounts ranging from about 40 mg to about 1,400 mg, preferably from about 80 mg to about 1,050 mg. In another embodiment, the compositions contain from about 50 % to about 80 % w/w lactose monohydrate, preferably from about 60 % w/w to about 75 % w/w. Lactose adduct formation is less than 3 % w/w, more preferably less than 2.5 % w/w.
• microcrystalline cellulose In a preferred embodiment of the invention containing memantine, microcrystalline cellulose (MCC) is used as a filler.
• MCC microcrystalline cellulose
• MCC is used as an additional filler, present in amounts ranging from about 13 mg to about 420 mg, preferably from about 25 to about 315 mg per unit dose. In one embodiment, the MCC is present in amounts from about 10 % w/w to about 35 % w/w, preferably from about 18 % w/w to about 22 % w/w.
• the MCC is used as a filler in the absence of lactose monohydrate, the MCC is present in an amount ranging from about 50 mg to about 1,600 mg, preferably from about 100 mg to about 1,200 mg per unit dose.
• compositions contain from about 20 % w/w to about 95 % w/w microcrystalline cellulose; more preferably from about 60 % w/w to about 90 % w/w.
• the microcrystalline cellulose provides the desired dissolution profiles with acceptable or improved formulation and processing properties.
• these microcrystalline cellulose based formulations contain disintegrants. Disintgrants are starch-based, cellulose-based or pyrrolidone-based excipients, or based on a derivative of any of the foregoing, in amounts ranging from about 0.2 to 10 % w/w.
• excipients such as talc (an anti-adherant), starch, dicalcium phosphate, mannitol, croscarmellose sodium, colloidal silicon dioxide, sodium starch glycolate can also be used in combination.
• Use of the disinetgrants or soluble fillers allow for rapid disintegration of tablets exposing large surface area and the drug leading to faster dissolution of the drug.
• the dosage forms contain excipients that form less than 3.0 % adduct, preferably less than 2.5%, even 0% in lactose-free formulations.
• substances such as memantine and neramexane adducts result from a Maillad reaction.
• Adducts such as the lactose or other reducing sugar adducts, may form with the amines in adamantane derivatives.
• Tablets in accordance with this invention can be prepared by conventional mixing, comminution, and tabletting techniques that are well-known in the pharmaceutical formulations industry.
• the immediate-release tablet for example, may be fabricated by direct compression by punches and dies fitted to a rotary tabletting press, ejection or compression molding, granulation followed by compression, or forming a paste and extruding the paste into a mold or cutting the extrudate into short lengths followed by compression.
• the immediate release component may be applied as a coating over the core by spraying, dipping, or pan- coating, or as an additional layer by tabletting or compression.
• the process used for preparing tablets is direct compression of the blend.
• lubricants When tablets are made by direct compression, the addition of lubricants may be helpful and is sometimes important to promote powder flow and to prevent "capping" of the tablet (the breaking off of a portion of the tablet) when the pressure is relieved.
• Useful lubricants are magnesium stearate and hydrogenated vegetable oil (preferably hydrogenated and refined triglycerides of stearic and palmitic acids).
• magnesium stearate is used as a lubricant in an amount from about 0 mg to about 6 mg, preferably from about 0.3 mg to about 4.0 mg.
• the compositions contain from about 0 % w/w to about 2 % w/w magnesium stearate; more preferably from about 0.2 % w/w to about 0.5 % w/w magnesium stearate. Additional excipients may be added to enhance tablet hardness, powder flowability, and to reduce tablet friability and adherence to the die wall.
• Tablet hardness is linearly affected by different compression forces, shape and size of the tablet.
• compression forces increase (kN)
• Kp tablet hardness
• hardness values range from about 3 to about 40 Kp, more preferably from about 4 to about 30 Kp.
• the logo and product identification de-bossing was "picked” making it difficult to read and aesthetically less pleasing.
• the picking was eliminated without affecting dissolution at 30 minutes (see Example 1).
• the plasma concentration of the dose proportional immediate release memantine formulations have a time of maximum plasma concentration (T max ) in human patients ranging from between about 3 to about 7 hours, more often averaging between about 4 to about 6 hours, and an in vitro release rate of more than about 80 % in about 60 minutes, more preferably in about 30 minutes.
• the plasma concentration of the dose proportional immediate release formulations of neramexane have a time of maximum plasma concentration (T max ) ranging from between about
• the pharmaceutical formulations of the present invention allow for dose-proportional compositions and the modification of the C max by changing the strength of the formulation without substantially affecting the T max of the drug.
• the 30-minute immediate release formulations described in the present invention provide the desired T max without compromising the initial peak (C max ), which is characteristic of memantine or neramexane salts.
• a long Ti/ 2 allows for either twice a day, or preferably once a day, administration for an immediate release dosage form and achieves a relatively high C max which is considered essential for the pharmacological efficacy of the product.
• the C max for 20 mg memantine (administered at two 10 mg tablets 4 hours apart) would fall within the range of about 15 to about 40 ng/ml, with an average value of about 25 ng/ml.
• the memantine or neramexane dosage form is administered twice a day, administrations being approximately 4 hours apart, the average T max is about 8 hours ⁇ 2 hours.
• the dose proportionality allows up-titration beginning with lower doses for patient using an essentially identical formulation composition and varying essentially only the weight content of memantine or neramexane to achieve different strengths.
• an immediate release pharmaceutical composition is provided for the once daily administration or, if preferred, twice per day, of memantine or a pharmaceutically acceptable salt thereof, preferably its HCl salt, to a human or animal subject.
• an immediate release pharmaceutical composition is provided for the once daily administration or, if preferred, twice per day, of neramexane or a pharmaceutically acceptable salt thereof, preferably its mesylate salt, to a human or animal subject.
• the rapid dissolution profile of the tablets enables drinkable solutions for patients unable to ingest tablets.
• the memantine and neramexane formulations of the invention are suitable for the treatment of CNS diseases, including but not limited to the treatment of Alzheimer's disease, Parkinson's disease, AIDS dementia (U.S. Patent No. 5,506,231, see also Parsons et al., Neuropharmacology 1999 Jun;38(6):735-67), neuropathic pain (U.S. Patent No. 5,334,618), cerebral ischemia, epilepsy, glaucoma, hepatic encephalopathy, multiple sclerosis, stroke, depression (U.S. Patent No. 6,479,553), tardive dyskinesia, malaria, Borna virus, Hepatitis C (U.S. Patent Nos. 6,034,134 and 6,071,966).
• CNS diseases including but not limited to the treatment of Alzheimer's disease, Parkinson's disease, AIDS dementia (U.S. Patent No. 5,506,231, see also Parsons et al., Neuropharmacology 1999 Jun;38(6):735-67),
• the present invention further provides a method for the therapeutic or prophylactic treatment of CNS disorders in a human or animal subject, the method including administering to the subject a composition in accordance with the present invention.
• adduct formation refers to the formation of a compound with a particular formulation of a composition by a solid phase reaction.
• lactose adduct formation may occur with formulations containing lactose. Such adduct formation detracts from the efficacy of the product and increases the risks of other side effects.
• a “therapeutically effective amount” means the amount of a compound that, when administered to a mammal for treating a state, disorder or condition is sufficient to effect such treatment.
• the “therapeutically effective amount” will vary depending on the compound, the disease and its severity and the age, weight, physical condition and responsiveness of the mammal to be treated.
• a therapeutically effective amount of memantine is an amount effective to treat CNS disorders, including Alzheimer's disease or Parkinson's disease. Other uses include, but are not limited to, the treatment of dementia and depression.
• the effective amount of the drug for pharmacological action depends on the disease itself, e.g., in Alzheimer's disease, the patient is initially given a 5 mg dose and the dosage is progressively increased to 10 mg twice a day to 20 mg once a day. Similar up-titrations but starting from higher base amounts (e.g., base values starting at about 12 to about 15 mg, titrating up to about 80 mg) are useful for pain relief, e.g., neuropathic pain. Such titration may be facilitated by providing a selection of tablets representing standard or common doses, for example, 5mg, 10 mg, 15 mg, 20 mg, 40 mg and 80 mg doses of active substance. Therefore, it is important to have a dose proportional formulation.
• the term "pharmaceutically acceptable” refers to biologically or pharmacologically compatible for in vivo use, and preferably means approved by a regulatory agency of the Federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, and more particularly in humans.
• the term “treat” and its derivatives are used herein to mean to relieve or alleviate pain in a hypersensitive mammal or in a mammal suffering from a CNS disorder, e.g., dementia or Parkinson's disease.
• the term “treat” may mean to relieve or alleviate the intensity and/or duration of a manifestation of disease experienced by a subject in response to a given stimulus (e.g., pressure, tissue injury, cold temperature, etc.).
• a given stimulus e.g., pressure, tissue injury, cold temperature, etc.
• the term “treat” may mean to relieve or alleviate cognitive impairment (such as impairment of memory and/or orientation) or impairment of global functioning (activities of daily living, ADL) and/or slow down or reverse the progressive deterioration in ADL or cognitive impairment.
• the term “treat” also denotes to arrest, delay the onset (i.e., the period prior to clinical manifestation of a disease) and/or reduce the risk of developing or worsening a disease.
• the term “protect” is used herein to mean prevent delay or treat, or all, as appropriate, development or continuance or aggravation of a disease in a subject.
• the dementia is associated with a CNS disorder, including without limitation neurodegenerative diseases such as Alzheimer's disease (AD).
• AD Alzheimer's disease
• picking refers to the detachment of material (such as a film fragment) from the surface of a tablet upon contact with another object and its adherence to the surface of the other object (such as another tablet or a tooling) (See Pharmaceutical Dosage Forms: Tablets Volume 3, edited by H. A. Lieberman and L. Lachman, pp. 101 and 272 (Marcel Dekker, Inc. 1982)). Picking may occur, for example, when tablets are compressed or tumbled. The material removed may obscure or obliterate logos, monograms, lettering, and numbering which were intended to appear on the surface of the tablet.
• dose proportional refers to the relationship between the dose of a drug and its bioavailability. For example, in the present invention, twice as much of the same composition to make a dosage form that will deliver twice the drug will provide the same bioavailability (i.e., AUC and C max ) as one dose of the dosage form.
• AUC and C max bioavailability
• the term “about” or “approximately” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, “about” can mean within 1 or more than 1 standard deviations, per practice in the art. Alternatively, “about” with respect to the compositions can mean plus or minus a range of up to 20%, preferably up to 10%, more preferably up to 5%. Alternatively, particularly with respect to biological systems or processes, the term can mean within an order of magnitude, preferably within 5-fold, and more preferably within 2-fold, of a value.
• use environment when applied to the formulations means the gastric fluids of a patient to whom the formulation is administered or simulated dissolution media.
• the present example describes the process of developing memantine hydrochloride immediate release tablets in 2.5, 5, 10, 15, 20, 40, 60, and 80 mg dosages. Materials and Methods
• Tables 1 and 2 provide the makeup of tablets with lactose and contain the same data expressed respectively in absolute (mg) or relative (% w/w) terms.
• Tables 3a - 3c and Table 4 also provide the makeup of tablets without lactose and contain the same data expressed respectively in absolute (mg) or relative (% w/w) terms.
• Core weight may be adjusted with fillers to +/- 10% depending on filler densities.
• Prosolv® is a mixture of microcrystalline cellulose and colloidal silicone dioxide
• 'Core weight may be adjusted with fillers to +/- 10% depending on filler density. ** Colloidal silicon dioxide may not be used.
• Table 4c For the dose proportional formulations of Table 3c, the percentage w/w for each of the active ingredient and excipients are identified in Table 4. Table 4. Weights in % w/w of tablet (lactose free) all strengths, including high drug load)
• Test batches of each of the tablets were prepared according to the process outlined below.
• Blend for Tabletting (lactose/MCC). Approximately half of the amount of microcrystalline cellulose and active drug was placed into a 20 ft 3 cone blender. Colloidal silicon dioxide was screened with the remainder of the microcrystalline cellulose through about 0.71 mm screen and added to the 20 ft 3 cone blender. The components were mixed for 6 minutes with the intensifier bar off. The lactose monohydrate (when called in the formula) and talc were screened through about 0.71 mm and added to the cone blender. The blender contents were mixed for 20 minutes with the intensifier bar off. The magnesium stearate was screened through about 0.8 mm filter and was added to the cone blender. The mixture was blended for an additional five minutes with the intensifier bar off.
• MCC microcrystalline cellulose
• active drug was placed into a 20 ft 3 cone blender. Colloidal silicon dioxide was screened with the remainder of the microcrystalline cellulose through about 0.71 mm screen and added to the 20 ft 3 cone blender. The components were mixed for 6 minutes with the intensifier bar off. The lac
• Tests were also conducted to study the effect of coating on dissolution and stability. Tablets were coated with Opadry (containing hydroxypropyl methylcellulose) material. A dissolution testing apparatus at 100 rpm was used to generate results. Alternate dissolution methods, e.g. 50 rpm using appropriate USP apparatus is also acceptable. Samples were collected after various levels of weight gain (based on amount of coating) and tested for dissolution at 15, 30, and 45 minutes. To determine the stability, coated tablets were put in a chamber under 40°C/75%RH accelerated conditions in an open dish for three months. Dissolution testing was carried out at 15, 30, and 45 minutes. Near IR Spectroscopy.
• a near infrared (near IR) for memantine immediate release formulation was performed with Infrared Chemical Imaging System (Spectral Dimension, Olney, MD). The tablet cross-section was measured, and single channel image at 1692 nm was used as a marker for memantine. The memantine rich domain was measured showing the distribution of the active ingredient. Different lots of memantine immediate release tablets were analyzed in triplicate. The analysis of data showed that memantine distribution among different lots was similar.
• Tablet friability was tested since the product was film-coated to mask the characteristic taste of the drug. Generally, the friability values were very low, indicating good mechanical integrity for the tablets. Tablet content was reviewed for uniformity, and in all cases tablets had low variability in content.
• Memantine HCl is a highly soluble and highly permeable drug. A target dissolution of no less than 80% in 30 minutes was desired in order to support a Biopharmaceutical Classification System (BCS) Class 1 classification for the drug. Tablets also showed rapid dissolution (greater than 80% in 30 minutes) even at very high hardness (20 Kp for 20 mg tablets).
• BCS Biopharmaceutical Classification System
• the present example presents the bioavailability of immediate release memantine tablets as compared to modified release memantine tablets.
• the study design in the present example was a 57-day single-center, open-label study in 24 young healthy subjects, ages ranging from 18 to 35 years old. Subjects underwent a screening evaluation consisting of a complete medical history, complete physical examination with vital signs, 12-lead ECG, clinical laboratory evaluations, consisting of a CBC (including differential), clinical chemistry, urinalysis, RPR/VDRL, Anti HIV 1 and 2 tests, drugs of abuse screen (including alcohol and nicotine), Anti-HCV and HbsAg. Female subjects had a ⁇ -hCG serum pregnancy test performed at screening and a urine pregnancy test on Day -1.
• Inclusion criteria included informed consent, normal physical examination, healthy adults between 18 and 35 years of age, non-smokers, within 15% of ideal body weight in relation to height, and a sitting pulse rate of not less than 50 beats per minute by palpitation, and a heart rate of not less than 50 beats per minute as recorded by ECG.
• Exclusion criteria included hypersensitivity to memantine or other NMDA antagonists, presence of any clinically significant disease, sitting systolic blood pressure greater than 180 mmHg or less than lOOmmHg or a sitting diastolic blood pressure greater than 100 mmHg or less than 60 mmHg at screening, significant ECG abnormalities, history of alcohol or substance abuse, positive tests to drugs of abuse, consumption of caffeine within 48 hours or alcohol within 72 hours prior to testing, participation in other clinical investigation within 30 days of study, clinical conditions associated with memantine, concomitant medications, or females breastfeeding.
• There were three treatment regimens including an immediate release (IR) memantine HCl
• the modified release formulations contained different compositions to achieve release rates > 70 % drug release in about 6 hour and about 12 hours.
• the subjects received three treatments on study days 1, 22, and 43 in a crossover manner separated by a 21 -day washout period based on randomized treatment sequences.
• the immediate release treatment was administered on Day 1 at 0800 and 1200 hours.
• the modified release treatments were administered on Day 1 at 0800 hours. After the washout periods, the subjects were crossed over to the other treatment (MR or IR).
• Formulations B and C are discussed in detail in co-pending application filed simultaneously with the present application, Attorney Docket no. 03269/1200817-US1.
• Subjects were admitted into a non-smoking environment at approximately 1900 hours on Days -1, 21, and 42. There were a total of six overnight stays for each subject (Days -1, 1, 21, 22, 42 and 43). Subjects were subjected to diet and fluid control and received no concomitant medications.
• Blood samples for the determination of memantine concentration were collected by a qualified phlebotomist using pre-chilled 5 mL green top Vacutainer® tubes (containing sodium heparin as an anticoagulant). Approximately 5 mL of blood were collected directly into pre-chilled 5-mL green top Vacutainer ® tubes (containing sodium heparin) following dosing on Days 1, 22, and 43. Blood samples were centrifuged within 30 minutes from the time of draw at 2,500 g for 10 minutes at 4 0 C and the plasma was harvested and transferred into pre-chilled, Forest coded polypropylene tubes. The samples were then flash frozen in an isopropyl alcohol/dry ice bath and stored in a - 7O 0 C freezer.
• Bioanalytical procedures The bioanalytical procedure used to measure the plasma memantine concentrations was validated to demonstrate accuracy, linearity, reproducibility, and precision of the analytical procedures.
• An LC/MS/MS (liquid chromatography/mass spec/tandem mass spec) method was developed for the determination of memantine in human plasma. After the addition of 10 ng of [ 2 H 6 ] memantine internal standard and 0.5 M sodium carbonate buffer to plasma standards and samples, the compounds were extracted with ethyl acetate. The organic layer was isolated and dried at room temperature under the vacuum in a sample concentrator (Savant). The dry residue was analyzed after reconstitution in mobile phase.
• the components of the reconstituted samples were separated on a Zorbax SB-C8 column (15O x 4.6 mm, 3.5 ⁇ m) and detected by atmospheric pressure chemical ionization (APCI) with a selected reaction monitoring (SRM) positive ion mode.
• the SRM used precursor -> positive product ions of m/z 180 -> 163 and m/z 186 - ⁇ 169 to monitor memantine and its internal standard, respectively.
• the protonated molecular ions of memantine and [ 2 H 6 ] memantine are the precursor ions for the SRM mode.
• the peak height ratio of memantine product ion to that of its internal standard was the response used for quantification.
• the plasma standards of the method validation showed accuracy within ⁇ 8.2% deviation and precision did not exceed 7.6% CV. Accuracy for the determination of memantine in plasma quality controls was within ⁇ 8.8% deviation with a precision not exceeding 9.8% CV.
• the lower limit of quantification of the method was 0.5 ng/mL.
• Pharmacokinetic analysis Pharmacokinetic parameters were estimated using WinNonlin (version 3.3, Pharsight Corporation, Mountain View, CA). The following parameters were determined from the plasma concentrations of memantine following single dose administration: the area under the plasma concentration time curve (AUC 0-t , AUCo -24 , and AUCo- ⁇ ), maximum plasma concentration (C max ), time of maximum plasma concentration (T max ), elimination half-life (T 1Z2 ) and mean residence time (MRT). Maximum plasma concentrations (C max ) and the time of the maximum concentration (T max ) for memantine were determined by observation.
• the first-order rate constant, ⁇ z describing the terminal decline in plasma was estimated by WinNonlin (version 3.3) using log-linear regression of the terminal linear phase of the mean plasma concentration-time curves of memantine.
• Ci was the plasma concentration at the corresponding sampling time point tj.
• AUC 0-24 , AUC 0-00 , t !/2 , and MRT were provided for subjects who completed the study.
• the present example demonstrates the makeup of 30-minute immediate release memantine tablets, with and without lactose monohydrate.
• the methods of making the tablets are the same as those disclosed in Example 1. Specifically, the tablets are made of the following active components, coating agent, and other excipients as presented below in Tables 9 and 10. Tables 9 and 10, summarizing the tablets with lactose monohydrate, contain the same data expressed respectively in absolute (mg) or relative (% w/w) terms.
• Tables 11 and 12 summarizing the tablets without lactose, contain the same data expressed respectively in absolute (mg) or relative (% w/w) terms.
• Figures 4, 5, 6, 7, and 8 show dissolution of 30 minutes IR tablets for 5 mg, 10 mg, 15 mg, two lots of 20 mg and 80 mg respectively for the formulation containing lactose monohydrate and MCC.
• Figure 9 shows the dissolution of 5 mg and 20 mg lactose-free formulations.
• another lot of 20 mg shows 15 minutes is about 65 % at initial time point, but greater than 80 % on stability. This variation is lot to lot variation.
• the results show that greater than 80 % of the drug is released in 30 minutes and in many instances greater than 80 % of the drug is released in 15 minutes.
• Adduct Formation An adduct is formed as a result of reaction between memantine with lactose monohydrate and similar excipients, known as reducing sugars. The adduct is not formed in lactose-free/MCC alone formulations. The adduct formation is detected using HPLC method with an Evaporative Light Scattering Detector. The product stored at ambient conditions over 40 months contained the adduct level of up to about 2.5 %. The adduct data are presented in Table 13.
• adduct level of less than about 3 %, preferably less than about 2.5 % are qualified in accordance with ICH guidelines Q3B(R), FDA Guidelines, Rockville, MD.

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